An external factor can also induce biases and shift the distributions. It is important to note that all images are acquired using sensors and pre-processed afterwards, potentially introducing defects to the images. In addition, their storage may require to compress the information they contain in many different ways. All this makes for a type of data with a considerable variability depending on the quality of the sensors, pre-processing pipeline and compression method.
This will be illustrated in the application of Section , where an automatic pre-processing scheme induces a bias in pseudo-color satellite images. In medical image analysis, external factors such as age affect the size of the organs but is also a causal factor to some diseases as analyzed in [1]}, for instance.
